Epidemiology of mesothelioma on Walcheren Island

Our plain-English summary of Epidemiology of mesothelioma on Walcheren Island, by J. Stumphius (British Journal of Industrial Medicine, 1971).

The study

• Author: J. Stumphius
• Journal: British Journal of Industrial Medicine
• Published: 1971;28(1):59-66
• Cited by: 57 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 001377).

Abstract

Stumphius, J. (1971). Brit. J. industr. Med., 28, 59-66. Epidemiology of mesothelioma on Walcheren Island. The chance finding of asbestos bodies without `asbestosis' in the lungs of a shipyard worker who had not worked directly with asbestos led to this investigation into the relationship between asbestos bodies in the sputum, occupation, and mesothelioma in the shipyard at Vlissingen on Walcheren Island. Examination of the sputum from a sample of 277 shipyard workers from various occupation groups (excluding insulation workers and others known to work continuously with asbestos) showed `asbestos' bodies to be present in 60%. The frequency varied from 39% in workers with no obvious exposure to asbestos dust to 100% among those with slight but definite exposure. By repeating the analysis using the occupations 5 to 10 years previously it was found that many of the workers currently employed in occupations not exposed to asbestos who had asbestos bodies in their sputum had been exposed in the past. Between 1962 and 1968, 25 cases of mesothelioma were discovered on Walcheren; of these, 22 cases had been employed in the shipyard at some time and their actual job was known in all but one case. The shipyard employs approximately 3 000 men so that the attack rate for mesothelioma was approximately 100 per 100 000 males per year. For Dutch provinces with heavy industry the rate is 1·0 per 100 000 per year. For the different occupational categories within the shipyard the rates varied from approximately 50 for `clean work' to 280 for men with some exposure to asbestos dust. Asbestos insulation workers were not included in the study and no cases of mesothelioma came from that occupational group.

In plain English

The author studied workers at the Royal Schelde shipyard, Vlissingen, Walcheren Island, Netherlands. Subcontracted insulation workers were excluded. Sputum from 277 employees was examined for asbestos bodies; workers were grouped by exposure to iron fumes, rust and asbestos dust. Asbestos bodies were found in 160 (57.8%), including every man examined in the group with rust and some asbestos exposure. Classified by jobs 5 to 10 years earlier, positives in the 'clean work' group fell to 26%. From 1962 to 1968, 25 mesotheliomas were diagnosed on the island (19 pleural, 4 peritoneal, 2 both); 22 of these patients had worked at the shipyard. The estimated rate for all shipyard workers was about 100 per 100,000 men per year, and 230 and 280 in two groups with some asbestos exposure. The national rate in Holland, for primary pleural tumours only, was 0.63 per 100,000 men per year in 1958 to 1965. The author concluded that asbestos bodies and mesothelioma were more frequent among workers exposed to asbestos dust. The author noted that the local and national figures were not strictly comparable.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Sputum survey of current shipyard workers combined with a local case series of mesothelioma, with approximate attack rates calculated by occupational exposure group
• Who was studied: Employees of the Royal Schelde shipyard, Vlissingen, Walcheren Island, Netherlands. Sputum was examined from 277 employees over a five-year period. The workforce was 3,102 men on 2 September 1967. Mesothelioma cases were those diagnosed on Walcheren in 1962 to 1968 (25 cases). Insulation workers were excluded.
• Exposure: Asbestos dust released during insulation work carried out by a subcontractor while ships were being finished or repaired, plus exposure to iron fumes and rust. Workers were placed in five groups (I iron vapour; II rust and some asbestos; III iron vapour and rust; IV some asbestos but little iron; V clean work). No worker studied was regarded as heavily exposed.
• Main results:
  • Asbestos bodies were found in the sputum of 160 of 277 employees examined (57.8%).
  • Classified by current occupation, every sputum sample from group II (rust and possible asbestos exposure) contained asbestos bodies.
  • Reclassified by occupation 5 to 10 years earlier, the 63 positives in the clean work group (39%) dropped to 33 (26%).
  • Using past occupation, the percentage of positive sputa in group V differed significantly from groups I to IV (p less than 0.001). Groups I to IV also differed significantly from one another (p less than 0.05).
  • Of the 25 mesothelioma cases diagnosed on Walcheren in 1962 to 1968, 22 were histologically confirmed. Nineteen tumours originated in the pleura and 4 in the peritoneum. In 2 cases the tumour involved both and the site of origin could not be decided.
  • Of the 25 mesothelioma cases, 22 had been employed in the shipyard at some time, and 17 were employed there when their symptoms began.
  • Numerous asbestos bodies were found in all 11 cases that had a necropsy (post-mortem examination).
  • Relating cases to the workforce on 2 September 1967 gave seven-year attack rates of 1.6% in group II and 1.9% in group IV, the two groups with some asbestos exposure. Rates were 0.6% in group I, 0.9% in group III and 0.32% in group V, with a mean of 0.68% for all workers.
  • The attack rate for all shipyard workers was about 100 per 100,000 men per year.
  • Rates in the two groups with some asbestos exposure were 230 per 100,000 per year (group II) and 280 per 100,000 per year (group IV).
  • For comparison, the national rate for primary pleural tumours in Holland was 0.63 per 100,000 men per year in 1958 to 1965.
  • No mesotheliomas occurred among the subcontracted insulation workers, although asbestosis was found among them.
• The authors' conclusion: The author concluded that asbestos bodies in sputum and mesothelioma were more frequent among shipyard workers exposed to asbestos dust at work. The author also stated that all groups of shipyard workers appeared to have had some exposure and an excessive incidence of mesothelioma.
• Limitations the authors state:
  • The intensive local search for cases and differences in diagnostic criteria mean that the local and national rates are not strictly comparable.
  • Information on workers' occupations more than 10 years before the investigation was incomplete.
  • Because the incubation period may be 30 to 40 years, directly relevant information about past shipyard employment was not available.
  • Rates by exposure group are only approximate, because cases were related to the workforce employed at the time of the study.

Topics

Medical terms in this study, explained in our Lexicon: Epidemiology, Mesothelioma, Asbestos Bodies, Sputum, Insulator.

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